1. Field
Embodiments of the present invention relate to a solenoid valve for a brake system and a manufacturing method thereof, to assure easier manufacture and lower manufacturing costs than the related art.
2. Description of the Related Art
A general vehicular anti-lock brake system is designed to prevent wheel lockup when braking hard by controlling braking pressure applied to wheels based on sensed tire slip.
This assures directional stability and steering control of wheels without tire slip during braking and consequently, safe braking.
This type of brake system includes a plurality of solenoid valves that opens or closes flow-paths of brake hydraulic lines to control braking pressure. Solenoid valves may be classified into normally opened type solenoid valves that are normally kept in an opened state, and normally closed type solenoid valves that are normally kept in a closed state.
FIG. 1 is a sectional view illustrating a conventional normally closed type solenoid valve. The valve is press-fitted into a bore 14 of a modulator block 13 in which flow-paths of a brake system are defined. The valve includes a hollow valve housing 1 having an inlet 3 and an outlet 4 for fluid flow.
A cylindrical sleeve 6 is inserted into one end of the valve housing 1 and in turn, an armature 5 is movably received in the sleeve 6. A valve core 7 is fitted into an open end of the sleeve 6. The valve core 7 serves not only to close an opening of the sleeve 6, but also to move the armature 5. The armature 5 is moved to open or close a first orifice 8a of a valve seat 8. For this, the armature 5 has an opening/closing portion 5a extending toward the valve seat 8 through a hollow 2 of the valve housing 1.
A return spring 9 is interposed between the armature 5 and the valve core 7. The return spring 9 presses the armature 5 to allow the armature 5 to normally close the first orifice 8a. An excitation coil assembly 10 is installed around the sleeve 6 and valve core 7 for movement of the armature 5. A second orifice member 11 having a second orifice 14a is inserted in the valve housing 1, and an O-ring 12 is fitted around the valve housing 1 to seal a gap between the valve housing 1 and an inner surface of the bore 14. Also, a filter member 15 having a filter is fitted around the valve housing 1.
In operation of the above-described solenoid valve, when power is applied to the excitation coil assembly 10 to generate magnetic force, the armature 5 is moved toward the valve core 7 by the magnetic force, thus operating to open the orifice 8a of the valve seat 8. On the other hand, no magnetic force is exerted when no power is applied to the excitation coil assembly 10 and thus, the armature 5 operates to close the orifice 8a by elasticity of the return spring 9.
As described above, the conventional solenoid valve for a brake system is configured such that the valve seat is provided separately from the valve housing and thus, is press-fitted in the valve housing. The valve housing has been mainly formed by forging and therefore, has a great number of components. This results in difficult manufacture and higher production price.